US President Joe Biden initially loosened the restrictions on how Ukraine could use US-provided munitions to give it another option to defend the eastern city of Kharkiv from a relentless barrage of Russian missiles.
Since the beginning of Russia's 2022 invasion, the US had maintained a policy of not allowing Ukraine to use the weapons it provided to hit targets inside Russia for fear of further escalating the war.
Russia has been firing on Ukrainian targets from inside its border, treating its territory as a "safe zone," Pentagon press secretary Major General Pat Ryder said.
"As we see those forces conducting those types of operations from across the border, we've explained Ukraine can and does have the right to fire back to defend themselves," Ryder told reporters.
The Pentagon said the additional permissions are not a new policy.
"This is not about geography. It's about common sense," spokesman Army Major Charlie Dietz said.
Ukrainian armed forces can use US air defence systems to take out Russian planes, officials say. (AP PHOTO)
"If Russia is attacking or about to attack from its territory into Ukraine, it only makes sense to allow Ukraine to hit back against the forces that are hitting it from across the border."
"Additionally, they can use air defence systems supplied by the United States to take Russian planes out of the sky, even if those Russian planes are in Russian airspace, if they're about to fire into Ukrainian airspace," Dietz said in a statement.
The White House also announced on Thursday that it is rushing delivery of air defence interceptor missiles to Ukraine by redirecting shipments planned for other allied countries as the US scrambles to counter increased Russian attacks on Ukrainian energy infrastructure.
The US was already sending Ukraine a consistent stream of interceptors for its air defence systems, including for the Patriot missile batteries and the National Advanced Surface-to-Air Missile Systems, or NASAMS.
National security spokesman John Kirby told reporters that more was urgently needed as Russia's military has accelerated missile and drone attacks against cities and infrastructure centres ahead of winter.
The rushed shipments are expected to include hundreds of Patriot missiles.
